There is still a little confusion about what you mean and I think you are getting some terms mixed up. It is not clear from your post that the "original array" is indeed an array. It could be if declared like

my @originalArray = qw{D F Y I N G W};
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or it could be a space separated string like

my $originalString = q{D F Y I N G W};
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Your "output array" is not an array, it is a scalar containing a string. If your original array is an array you need to turn it into a string so you can search it. Do something like

my $stringToSearch = join q{}, @originalArray;
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However, if it already was a string with spaces in it, you need to remove those with a global replace

(my $stringToSearch = $originalString) =~ s{\s+}{}g;
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Once you have a contiguous string of letters you can do another global replace looking for "SEKAR" and using parentheses () which are regular expression memory. For example, if you do $string =~ m{(SEKAR)}; then if the match succeeds the string "SEKAR" will be placed in the special read-only variable $1 for later use. So you could now do

$stringToSearch =~ s{(SEKAR)}{<sometag>$1</sometag>}g;
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That will replace every occurrence of SEKAR in the string with <sometag>SEKAR</sometag>.

I hope this will give you enough pointers to get started.

Cheers,

JohnGG